Uncertainty persists whether long term exposure to air pollutants is associated with reduction in lung functions or increased chronic respiratory symptoms. A large number of recent studies have addressed the short term effects of air pollution, but the greater cost involved in collecting large amounts of individual data has limited the number of long term exposure studies available. The published studies of long-term health effects, such as the Harvard Six Cities study or the Seventh Day Adventist study, have been restricted to predominantly white populations. Minority populations may have greater exposure to pollutants, and have co-exposures or other risk (such as higher rates of asthma) that make them more sensitive to the potential adverse effects of air pollution. The study will merge measures of health status collected in the Third National Health and Nutrition Examination Survey (NHANES III) with air quality data from the U.S. Environmental Protection Agency files. NHANES III is a stratified random sample of the US population with over sampling of minorities, children under 5 years and elderly. Respiratory health status is determined by questionnaire, lung function tests, and physician examination. Data is also collected on other predictors of respiratory health which might confound or modify the association with air pollution. Air pollution exposures will be estimated for each individual surveyed based on routinely oriented air pollution monitoring stations weighted by the inverse square of the distance between the monitor and the subject residence. This study will test the hypothesis that long term air pollution exposure is associated with reduction in pulmonary function and increase in chronic respiratory symptoms in children and adults, that the impact of air pollution exposure is greater in minority populations, and that the effects of air pollution exposure are modified by atopy and antioxidants.